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The ABCL
family of languages
ABCL: An Object-Oriented Concurrent System
The tenet of our ABCL research project is to exploit both parallelism
and object orientation. Parallelism is ubiquitous in our problem
domains; parallelism is not only the source of computational power,
but also promotes structural simplicity/naturalness in design and
algorithm. Object-orientation accompanying parallelism, enhances
system modularity, flexibility, and safety. Such an approach, called
object-oriented concurrency, is summarized as follows:
- the software or algorithm to be designed/constructed is
represented as a collection of concurrently executable (concurrent)
objects, and
- the interaction among the system components is represented
solely as message transmissions among such objects.
A concurrent object models the functions and properties of an entity
appearing in a problem domain. It is an encapsulated (program) module
which contain data and the associated procedures to operate on the
data, and also perform message passing. Upon receiving a message, it
becomes active and executes a procedure specified by the message.
Message transmission may take place concurrently among objects, thus
enabling objects to be active in parallel. The basic mode of message
passing in our approach is asynchronous in the sense that an object
can send a message whenever it wants to, irrespective of the mode of
the receiver of the message. This expands the degree of parallelism
allowed in a system. We also assume that an object is able to create
new objects dynamically. The capability of dynamic object creation is
indispensable in modeling and representing complex, open systems
naturally. We believe that the asynchrony and this dynamicity are
fundamental in our approach. We developed a parallel computation
model ABCM/1 (An object-Based Concurrent computation Model 1) and its
associated description language ABCL/1 (An object-Based Concurrent
Language 1). ABCM/1 is based on our notion of "objects", while
ABCL/1 serves as a programming language in which systems and
algorithms are written based on objects defined in ABCM/1. From ABCM/1
and ABCL/1, our research project has stemmed mainly towards three
directions: theory, implementation/environment, and application. In
each direction, there are a number of research topics that have been
identified and investigated.